With regard to rotating machines for a generator, vehicle and general industrial use, miniaturization, weight reduction, and the increase of the capacity are required. As a means for miniaturization and weight reduction of the rotating machines, the increase of the current density can be cited, however, if the current density is increased, because the heat generation amount of a conductor increases when the capacity is same, high heat resistance is required for an insulating material used for a coil.
As the insulation treatment of an insulation coil and a stator coil used for a rotating machine, a single injection (impregnation) method and an integrated impregnation method are known in which a mica tape and an impregnating varnish are used.
(1) The single injection method is a method in which a dry mica tape is wound around a conductor formed into a specified shape and insulatingly sheathed to make an insulation coil unit, the impregnating varnish is injected (impregnated) in vacuum to the insulation coil unit, is thereafter further pressure-injected (impregnated), is heat-cured to make the insulation coil which is accommodated in an iron core slot and is fixed by under-insertion-piece liners, an insertion piece and the like to make a stator coil.(2) The integrated impregnation method is a method in which a dry mica tape is wound around a conductor formed into a specified shape and insulatingly sheathed to make an insulation coil unit, which is incorporated in an iron core slot, is fixed to inside the slot by under-insertion-piece liners, an insertion piece and the like, is connected in iron core ends for integration to make a stator unit, to which the impregnating varnish is pressure-injected in vacuum, and thereafter heat-curing is performed to make a stator coil.
As described above, according to the single injection method and the integrated impregnation method, because the impregnating varnish can permeate into the entire coil such as the conductor, the void which becomes a cause lowering the electric insulation property can be reduced, and electric insulation reliability becomes high. The insulating material applied to these insulation treatment methods is constituted of the impregnating varnish with the main components of an unsaturated polyester resin and an epoxy resin, and a dry mica tape formed of base material such as a film, mica paper, a binder resin with which the mica paper and the film base material are bonded to each other, and the like.
The heat-resisting property of the coil insulating material manufactured by the injection method depends on the heat-resisting property of the cured resin of the impregnating varnish used for the insulating material. With regard to the method in which the coil insulating material manufactured using the injection method is made highly heat-resistant by making the impregnating varnish highly heat-resistant, there are methods, for example, described in Japanese Published Unexamined Patent Application Nos. H1-4615 (patent document 1) and H9-316167 (patent document 2). According to the patent document 1 and patent document 2, the impregnating varnish in which the raw material excellent in the heat-resisting property such as a multifunctional epoxy resin and a multifunctional curing agent are used is employed. However, the multifunctional epoxy resin, the multifunctional curing agent and the like are solid or highly viscous in the ordinary temperature (25° C.), and the impregnating varnish blended therewith also becomes highly viscous in the ordinary temperature. Accordingly, the injection performance of the impregnating varnish for the gap between the inductors of the coil and the fine detail of the insulating material lowers, and therefore, for example, the impregnating varnish is used after being heated and the viscosity is lowered in injecting. Also, the impregnating varnish is used for injection to the coil repeatedly for many times. Accordingly, because the curing reaction progresses gradually when the impregnating varnish is heated in every injection as described above, periodical abandonment is required. As a result, in order to make the insulating material highly heat-resistant by the impregnating varnish described in the patent document 1 and the patent document 2, the problems of lowering of the injection performance and the increase of abandonment quantity arise.
On the other hand, there are methods of manufacturing a coil achieving continuous use at 200° C. or above in which the binder resin of the dry mica tape is made highly heat-resistant, and thereby peeling-off caused by deterioration and the like of the coil insulating material manufactured by the injection method in heat-curing is prevented. They are described in, for example, Japanese Published Unexamined Patent Application Nos. H3-77203 (patent document 3), H6-233485 (patent document 4), and H6-233486 (patent document 5). In the patent document 3, a multifunctional epoxy resin including 3 or more of p-(2,3-epoxypropoxy)phenyl groups is used solely or along with a phenolic curing agent as a binder resin of the dry mica tape, in the patent document 4, an unsaturated imide-based resin composition is used as a binder resin, in the patent document 5, an epoxy resin composition having a naphthalene skeleton is used as a binder resin, and thereby the effect described above is achieved. However, according to the patent documents 3 to 5, because the binder resin of the dry mica tape is solid, it is hard to be dissolved in the injected impregnating varnish, and therefore there is a problem that the curing reaction of the binder resin and the impregnating varnish becomes non-uniform. Also, according to the patent documents 3 to 5, the base material of the dry mica tape and the mica paper (mica layer) are constituted to be bonded by one binder resin.
In the patent documents 3 to 5, there is no description that a binder resin layer A bonding a base material and mica paper has a function of solely performing curing reaction and being cured inclusion of which is clearly described in the present invention. Further, in the patent documents 3 to 5, there is no description also that a second binder resin with a composition different from that of the binder resin is arranged on the surface of mica paper and allowing curing reaction with an impregnating varnish. Accordingly, it is obvious that, in the patent documents 3 to 5, there is no description on the constitution of using two binder resins with different composition as described in the present invention, and the constitution is not disclosed in which a binder resin layer A having functions of bonding mica paper and a base material before the curing reaction and curing the mica paper and the base material after the curing reaction and a binder resin layer B present on the surface of the mica paper and having a function of dissolving in and cure-reacting with the impregnating varnish are used.
The present invention has been made to improve the heat-resisting property of a coil insulating material manufactured by an injection method using a dry mica tape and an impregnating varnish, to improve the electric insulation property of insulation coils and a stator coil at a high temperature, and to miniaturize rotating machines. Also, the impregnating varnish is surely impregnated into a dry mica tape insulation layer and the like wound around a conductor, and thereby the insulation coils, stator and rotating machines excellent in the electric property can be provided.